Page:A Treatise on Geology, volume 1.djvu/155

 CHAP. VI. the form and arrangement, offers us the best analogies. The coral islands of the South Seas are in this respect very dissimilar.

The best, or rather the only, complete British series of these rocks is that of the Welsh border, of which the above section is a sketch: below is Mr. Murchison's summary.

On a careful examination of the vicinity of Ludlow, all the upper parts of the Silurian rocks may be perfectly traced and clearly discriminated: it is in the vale of the Towey (Dinevawr) that the lower formation is